Seventy-two poison gas shells left by the Imperial Japanese Army during World War II have been found at a factory site in Huiyang, Henan Province in central China, Xinhua News Agency said Tuesday.

The shells were discovered in early March, together with 130 conventional artillery shells, during excavation work. Workmen who dug up the shells said they released a stinging, white smoke.

Chinese bomb experts said there were five different types of gas shells at the site, according to Xinhua.

According to historical documents, Huiyang was occupied by the Japanese army from September 1938 until the end of the war in August 1945.

Last September, a joint Japan-China task force removed 10 poison gas shells abandoned by the army in Beian, Heilongjiang Province.

Japan says 700,000 chemical weapons are believed to have been abandoned in China, while China claims the number is 2 million.